Eduardo F. Marques

Abstract Polymeric hydrogels are traditionally employed as drug reservoirs in topical delivery, but they can also function as scaffolds for drug-loaded nanocarriers, enabling hybrid systems with enhanced performance. In this work, we report a thermo-adaptive hybrid hydrogel-composed of a block copolymer scaffold and a network of surfactant-based nano- and microtubes-which exhibits a mechanism herein termed inversely coupled thermogelation (ICT). The scaffold consists of Pluronic F127, a biocompatible triblock copolymer that transitions from micellar solution to a cubic liquid crystalline gel upon heating. The tubular network arises from the self-assembly of biomimetic lysine-derived surfactants. Crucially, when the block copolymer/surfactant hybrid is heated from 20 degrees C to 35 degrees C (approx. skin temperature), the surfactant tubes disassemble into micelles or vesicles, while the block copolymer forms the cubic phase. Accordingly, a tube-dominated gel evolves into a block copolymer-dominated gel through a gel-solution-gel sequence uniquely driven by the opposing thermal responses of the two constituents. This results in a hybrid system that is not only spreadable, self-healing, and mechanically robust, but also well-suited for sustained topical delivery. Imaging, calorimetry, and rheology provide detailed insights into the structure, phase transitions, and flow behavior of the hybrid system and its individual components. As a proof-of-concept, the gel enables slow, sustained release of a fluorescent model probe (carboxyfluorescein), exhibits excellent cytocompatibility, and promotes high cell internalization. Overall, this ICT-based strategy establishes a versatile and sustainable platform with strong potential for long-term topical drug delivery.

Abstract Stimuli-responsive surfactant self-assembly offers versatile opportunities to tailor colloidal structure and function through simple formulation strategies. Here, we report a photoresponsive catanionic vesicle system composed of the double-chained cationic surfactant didodecyldimethylammonium bromide (DDAB) and an anionic amphiphilic 2-hydroxychalcone derivative bearing a sulfonate headgroup (C8SCh). The self-assembly and phase behavior of the individual components and their mixtures are characterized, revealing a broad vesicle-forming compositional range. Notably, three molar fractions (xCh = 0.10, 0.20, and 0.80) yield dispersions composed exclusively of vesicles, enabling the formation of either positively or negatively charged vesicles using the same pair of molecular building blocks. Strong synergistic interactions between DDAB and C8SCh are evidenced by markedly reduced critical aggregation concentrations and negative interaction parameters. The incorporation of the chalcone photoswitch endows the vesicles with light responsiveness, inducing composition-dependent morphological rearrangements in both DDAB-rich and C8SCh-rich regimes. Under mildly acidic conditions (pH = 4.5), partial conversion of the chalcone to its flavylium form introduces an additional, independent stimulus that further modulates the structure of C8SCh-rich vesicles. This intrinsic charge tunability enables highly efficient, charge-selective electrostatic entrapment of both anionic and cationic molecular probes-carboxyfluorescein (CF) and doxorubicin (DOX), respectively-without the need for active loading strategies. Importantly, cargo release is selectively modulated by vesicle composition and external stimuli: light stimulation enhances the release of CF from DDAB-rich vesicles, while the combined action of acidification and irradiation significantly increases DOX release from C8SCh-rich vesicles. Overall, these results establish a simple catanionic system in which surface charge, morphology, and release behavior are jointly controlled by composition, light, and pH, offering a versatile and readily formulated platform with potential applications in controlled delivery.

Abstract Electrochemical energy conversion technologies are central to sustainable power generation, yet sluggish oxygen reduction reaction (ORR) kinetics remain a key limitation in alkaline fuel cells. Although Pt-based electrocatalysts are highly active, their cost and scarcity motivate the development of sustainable, carbon-based alternatives. Here, biochars derived from different parts of an abundant invasive plant, water hyacinth (WH), namely bulbs, wood and leaves, were prepared, screened, and evaluated as ORR electrocatalysts. Among them, bulb-derived biochar (WHB) showed the highest potential, and nitrogen doping produced the most pronounced enhancement. N-doped WHB exhibited an onset potential of 0.85 V, a limiting current density of-3.19 mA center dot cm-2, an electron transfer number of nO2 = 3.16 and a Tafel slope of 57 mV center dot dec-1, approaching Pt/C in activity metrics. XPS and Raman analyses linked these improvements to favorable nitrogen speciation-particularly graphitic N-and increased structural disorder. In parallel, layer-by-layer (LbL) hybridization with multi-walled carbon nanotubes (MWNTs) provided complementary insight into structure-performance relationships. Hybridization improved ORR activity when the base material was pristine WHB (among the nanocomposites, 3:1 WHB:N-MWNT performed best, with Eonset 1/4 0.81 V, jL =-3.37 mA center dot cm-2, nO2 = 3.12, and TS = 76 mV center dot dec-1), consistent with effective integration of porous biochar and conductive nanotube pathways. In contrast, adding MWNTs to already highly active N-WHB reduced performance, likely due to dilution of catalytic sites and disruption of active interfaces. Overall, this study demonstrates invasive biomass as a viable feedstock for high-performance, Pt-free ORR catalysts and highlights when chemical tuning versus hybrid assembly is most beneficial for catalyst design.

Abstract Hydroponics is an advanced agricultural technique that involves growing plants without soil. Instead, plants are cultivated in a nutrient-rich water solution that provides all the essential minerals they need to thrive, allowing plants to grow either with their roots directly in the solution or supported by inert substrates like pine bark, coconut husk fiber, and rice husk. The solid waste generated from hydroponic cultivation is valuable due to its low cost, abundance, biodegradability, and renewability. These residues are rich in lignocellulosic materials, which can be extracted and refined to produce cellulose and nanocellulose (NC). In this work, cellulose and nanocellulose were extracted from residues of coconut husk fiber and a mixture of pine bark and coconut husk fiber, used in tomato and strawberry hydroponics, respectively. The residues were ground, washed, and chemically treated to obtain cellulose and NC. The chemical process involved several stages: (i) acid treatment, alkaline treatment, and bleaching to isolate cellulose, and (ii) acid hydrolysis followed by ultrasonication to obtain NC. Both materials underwent characterization using various techniques such as TGA, DSC, XRD and FTIR-ATR, which confirmed very low levels of lignin and hemicellulose. Morphological characterization through SEM revealed the presence of micro- and nano-crystals in the cellulose and NC samples, respectively, highlighting the effectiveness of the extraction method. The high purity and quality of the extracted materials make them competitive with commercially available products, suitable for applications in healthcare, food packaging, and automotive industries, while supporting recycling and reuse principles.

Abstract Thermotropic ionic liquid crystals (TILCs) are ion-containing fluids forming upon heating between the crystalline and liquid phases of ionic amphiphiles. Bis(quaternary ammonium) gemini surfactants with general formula n-s-n—where n and s are the main tail and the spacer lengths, respectively—are able to form TILCs, but systematic studies on the effect of the spacer length are still lacking. Here, we investigated the possibility of tuning TILC formation by varying s for 14-s-14 gemini surfactants using an unusually wide range of spacers, from 2 up to 20 methylene groups (s = 2, 6, 8, 12, 14, 18 and 20). The thermal stability of these compounds was assessed by thermogravimetric analysis (TGA) and the thermodynamic parameters of the phase transitions (temperature, enthalpy and entropy changes) by differential scanning calorimetry (DSC), while TILCs were assigned by polarized light microscopy (PLM). X-ray diffraction (XRD) of the powder compounds was also carried out to provide insight into the solid phase packing. Notably, the isotropization temperature to the ionic liquid phase shows an inverted V trend with increasing s in the s = 2–12 range, and then increases linearly in the range s = 12–20. Smectic A liquid crystals form for all compounds, with 14-2-14, 14-12-14 and 14-14-14 displaying lower temperatures (approx. range 100–120 °C) than the rest. Overall, the results show that incrementally varying the spacer length affects the phase behavior, thermal stability, thermodynamic parameters of the thermotropic phase transitions, and solid-phase smectic d-spacings in a marked and complex manner, with several non-monotonic trends observed. Moreover, the spacer length can be selected to tune the formation of ionic liquid crystals, pointing to a fine balance between the main chain and spacer lengths. © 2025 Elsevier B.V., All rights reserved.